The Severe Chronic Neutropenia International Registry (the Registry) opened in 1994 to study the long-term safety and efficacy of granulocyte-colony stimulating factor (G-CSF) treatment for patients with congenital, cyclic and idiopathic neutropenia. The Registry initially evaluated hematological parameters, growth and development, consequence of pregnancy, and other important clinical events. The Registry is now an international research organization based at the University of Washington. In this grant, we request funding to continue the work of the Registry. In brief, the specific aims are: (1) To expand the longitudinal clinical database on patients with severe chronic neutropenia, (2) To expand a bank of biological materials to support genetic and molecular research and study the evolution of patients at risk to develop myelodysplasia and leukemia, (3) To serve as a resource to support clinical trials to improve therapy, (4) To serve as a educational resource for patients, families, physicians and other care providers, (5) To cooperate with researchers studying the other hematopoietic failure disorders. All of these efforts are directed toward improving understanding of the care of patients with severe chronic neutropenia.